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Quake shakes ocean floor around 6:50 a.m. PT

No tsunami warning issued

(CNN)A 6.5-magnitude earthquake shook the ocean floor about 100 miles off the northern California coast Thursday morning, causing weak to light shaking in coastal communities in parts of that state and Oregon, the US Geological Survey said.

The quake, centered about 102 miles west of Ferndale, California, happened around 6:50 a.m. PT.

Light shaking was reported from east central Oregon to areas a few dozen miles south of San Francisco, the USGS said.

No tsunami threat is expected from the quake, the Pacific Tsunami Warning Center said. There were no immediate reports of injuries or serious damage.

The quake led to inconveniences for some commuters in the San Francisco area. Bay Area Rapid Transit trains temporarily moved at a reduced speed after the temblor, leading to delays of about 10 minutes, the transit system's Twitter account said. The move was precautionary, CNN affiliate KGO reported.

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10 min delay system wide due to earlier seismic activity, trains are running at reduced speed.